The present invention relates generally to optical lenses and more particularly to flexible lenses for controlling optical properties by varying the pressure of a fluid within a chamber of the flexible lens.
Flexible optical lenses of the known art have largely been employed to provide a variable focal length for a given optical input. Generally, known art flexible lenses comprise a single chamber encapsulated by a flexible transparent membrane and filled with a gas, liquid, or other fluid. By changing the pressure of the fluid in the chamber, the shape of the flexible membrane also changes, thereby changing the focal length of the lens. With the single chamber, however, the flexible membrane is limited to providing a concave lens on both ends or a convex lens on both ends of the chamber.
Other known flexible lenses provide two independent chambers rather than a single chamber, such that a flexible membrane on each side of the lens flexes independent of the other flexible membrane. Therefore, one side of the lens may be concave and while the other is convex, and vice versa, along with various combinations thereof. For example, U.S. Pat. No. 3,161,718 to De Luca discloses a variable lens that has two fluid tight lens compartments enclosed by a flexible diaphragm on each end and separated by a clear separator disc. The variable lens further comprises two pressure actuators that independently control the amount of pressure in each compartment, and thus the amount of flex of each diaphragm. As a result, a variety of flexible lens combinations may be produced, as set forth in FIGS. 7A through 7H, to control the focal length of an optical input. Additionally, De Luca and other known flexible lenses are limited to a constant optical input wherein optical properties are exclusively controlled by the flexible membrane and/or the substance within the compartments.
With many optical applications, and more specifically with regard to fiber optic applications, a terminated bundle of fibers receives light from an optical input such as a collimated beam for subsequent transmission of the light in an optical system. An important aspect of transmitting light to the bundle involves providing a constant spot size output of the light to the face of the fibers such that each fiber receives approximately the same amount of light. In addition, the intensity distribution of the output must be substantially flat such that all of the fibers receive approximately the same intensity of light. Moreover, the angular distribution of the light must similarly be substantially uniform.
At times, the intensity of the optical input must be varied while still maintaining a constant spot size output, a substantially flat intensity, and a substantially uniform angular distribution in order to accommodate different fiber bundle sizes and different operating requirements of the fiber bundle. Unfortunately, flat intensity distributions and uniform angular distributions are difficult to produce with optical systems of the known art, primarily because an iris that adjusts the optical input has a limited minimum size. If the minimum size of the iris becomes smaller than the face of the fiber bundle, the fibers around the periphery of the bundle cannot receive the same amount of light.
Unfortunately, using a focused beam of light, i.e. output from a flexible lens of the known art, an approximate gaussian intensity distribution results across the face of a fiber bundle, which is not a flat intensity distribution. The intensity may be controlled using an iris, for example, or by changing the power output of a lamp. However, changing the power output of the lamp alters the intensity distribution and also the color temperature of the light. Accordingly, the color temperature may be maintained while the power output of the lamp is held constant by employing an iris with a variable aperture to control intensity. As a result, however, the spot size of the output changes and not all of the fibers in the bundle may receive an equal distribution of light or a substantially flat intensity distribution and a substantially uniform angular distribution.
Accordingly, there remains a need in the art for a flexible lens that provides a constant spot size output, a substantially flat intensity distribution, and a substantially uniform angular distribution across a target area while changing the intensity of an optical input. The flexible lens should operate without changing the color temperature of the light and should further be capable of enlarging or reducing the spot size output while maintaining a substantially flat intensity distribution and a substantially constant angular distribution.
In one preferred form, the present invention provides a flexible lens that comprises at least two chambers separated by a partition and encased in a flexible membrane. The flexible lens further comprises a regulator in communication with the chambers that controls the pressure therein. Further, an optical input is provided, which may be variable or constant depending on the desired output characteristics as further described below, which results in a constant or variable spot size output, respectfully, with a substantially flat intensity distribution and a substantially constant angular distribution across a target surface, e.g., the face of a fiber bundle.
The flexible membrane that encases the chambers further comprises a first lens portion adjacent the optical input and a second lens portion adjacent the target surface. In one form, the flexible membrane is one piece that encases both chambers. In another form, two separate membranes are used to cover each chamber, wherein the membranes are secured to a support structure or other similar device as may be contemplated by one of ordinary skill in the art.
The regulator that controls the pressure within the chambers causes the first lens portion and the second lens portion to flex in the same relative direction as one chamber receives positive pressure and the other chamber receives negative pressure. Accordingly, the pressure within one chamber is dependent on the pressure within the other chamber, wherein when one chamber receives positive pressure, the other chamber receives approximately the same amount of negative pressure, and vice versa.
In one form, a constant spot size output is generated with a substantially flat intensity distribution and a substantially uniform angular distribution using a variable optical input that operates in concert with the flexible membrane. Preferably, the optical input is varied using an iris diaphragm that defines a variable aperture. The iris diaphragm is disposed adjacent the first lens portion such that light from the optical input, e.g. a parabolic reflector, may be varied to the first lens portion. As the iris diaphragm closes to form a smaller aperture, the pressure in the chamber encased by the first lens portion is decreased and the pressure in the chamber encased by the second lens portion is increased. Accordingly, the first lens portion flexes inward and the second lens portion flexes outward to maintain a constant spot size output on the target area. Further, the intensity distribution is substantially flat, in addition to a substantially constant angular distribution.
In another form, the optical input remains constant while the pressure in the chambers is varied in order to produce a variable spot size output with a substantially flat intensity distribution and a substantially constant angular distribution. Accordingly, the pressure in the chamber encased by the first lens portion is decreased and the pressure in the chamber encased by the second lens portion is increased, wherein the first lens portion flexes inward and the second lens portion flexes outward, to increase the spot size. Similarly, the pressure in the chamber encased by the first lens portion is increased and the pressure in the chamber encased by the second lens portion is decreased, wherein the first lens portion flexes outward and the second lens portion flexes inward, to decrease the spot size.
The partition that separates the chambers is preferably a solid transparent material in order to maximize light transmission. Alternately, the partition may comprise a filter such that light may be filtered to a particular spectrum. Furthermore, the chambers may be filled with air, a liquid, or other substance as required in order to achieve the desired set of optical properties.
The regulator that controls pressure within the chamber in one form is a hydraulic cylinder that is vented to one chamber on one side of a piston and vented to the other chamber on the other side of the piston. When the piston moves within the hydraulic cylinder from one side to the other, one chamber receives negative pressure while the other chamber receives positive pressure. Alternately, the pressure may be regulated using drive mechanism such as a magnetic ring that is operable with the partition, wherein the partition slides laterally to cause negative pressure in one chamber and positive pressure in the other chamber.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.